Update state to keep track of this info.
Change function args as needed.
Make NumTx also an int64 for consistency.

otherwise, it is easy to get OutOfMemory panic (somebody can even expoit
this)

Refs #573

Fixes:
```
--- FAIL: TestHandshakeReplaySome (12.40s)
        replay_test.go:332: waited too long for tendermint to produce 6 blocks
```

to be consistent with Decode, which returns TimedWALMessage

We don't really need a separator unless we have complex structures
(rows, cells like RDBMS have https://www.sqlite.org/fileformat.html).

uint64 is considered dangerous. the details will follow in a blog post.

which was introduced in https://github.com/tendermint/abci/pull/130

and send them along with predefined

See https://github.com/tendermint/tmlibs/issues/45

```
==================
WARNING: DATA RACE
Write at 0x00c42d7605f0 by goroutine 844:
  github.com/tendermint/tendermint/consensus.(*ConsensusState).updateToState()
      /home/vagrant/go/src/github.com/tendermint/tendermint/consensus/state.go:465 +0x59e
I[11-14|22:37:28.781] Added to prevote                             vote="Vote{0:646753DCE124 1/02/1(Prevote) E9B19636DCDB {/CAD5FA805E8C.../}}" prevotes="VoteSet{H:1 R:2 T:1 +2/3:<nil> BA{2:X_} map[]}"
  github.com/tendermint/tendermint/consensus.(*ConsensusState).finalizeCommit()
      /home/vagrant/go/src/github.com/tendermint/tendermint/consensus/state.go:1229 +0x16a9
  github.com/tendermint/tendermint/consensus.(*ConsensusState).tryFinalizeCommit()
      /home/vagrant/go/src/github.com/tendermint/tendermint/consensus/state.go:1135 +0x721
  github.com/tendermint/tendermint/consensus.(*ConsensusState).enterCommit.func1()
      /home/vagrant/go/src/github.com/tendermint/tendermint/consensus/state.go:1087 +0x153
  github.com/tendermint/tendermint/consensus.(*ConsensusState).enterCommit()
      /home/vagrant/go/src/github.com/tendermint/tendermint/consensus/state.go:1114 +0xa34
  github.com/tendermint/tendermint/consensus.(*ConsensusState).addVote()
      /home/vagrant/go/src/github.com/tendermint/tendermint/consensus/state.go:1423 +0xdd6
  github.com/tendermint/tendermint/consensus.(*ConsensusState).tryAddVote()
      /home/vagrant/go/src/github.com/tendermint/tendermint/consensus/state.go:1317 +0x77
  github.com/tendermint/tendermint/consensus.(*ConsensusState).handleMsg()
      /home/vagrant/go/src/github.com/tendermint/tendermint/consensus/state.go:565 +0x7a9
  github.com/tendermint/tendermint/consensus.(*ConsensusState).receiveRoutine()
      /home/vagrant/go/src/github.com/tendermint/tendermint/consensus/state.go:523 +0x6d2

Previous read at 0x00c42d7605f0 by goroutine 654:
  github.com/tendermint/tendermint/consensus.validatePrevote()
      /home/vagrant/go/src/github.com/tendermint/tendermint/consensus/common_test.go:149 +0x57
  github.com/tendermint/tendermint/consensus.TestFullRound1()
      /home/vagrant/go/src/github.com/tendermint/tendermint/consensus/state_test.go:256 +0x3c5
  testing.tRunner()
      /usr/local/go/src/testing/testing.go:746 +0x16c

Goroutine 844 (running) created at:
  github.com/tendermint/tendermint/consensus.(*ConsensusState).startRoutines()
      /home/vagrant/go/src/github.com/tendermint/tendermint/consensus/state.go:258 +0x8c
  github.com/tendermint/tendermint/consensus.startTestRound()
      /home/vagrant/go/src/github.com/tendermint/tendermint/consensus/common_test.go:118 +0x63
  github.com/tendermint/tendermint/consensus.TestFullRound1()
      /home/vagrant/go/src/github.com/tendermint/tendermint/consensus/state_test.go:247 +0x1fb
  testing.tRunner()
      /usr/local/go/src/testing/testing.go:746 +0x16c

Goroutine 654 (running) created at:
  testing.(*T).Run()
      /usr/local/go/src/testing/testing.go:789 +0x568
  testing.runTests.func1()
      /usr/local/go/src/testing/testing.go:1004 +0xa7
  testing.tRunner()
      /usr/local/go/src/testing/testing.go:746 +0x16c
  testing.runTests()
      /usr/local/go/src/testing/testing.go:1002 +0x521
  testing.(*M).Run()
      /usr/local/go/src/testing/testing.go:921 +0x206
  main.main()
      github.com/tendermint/tendermint/consensus/_test/_testmain.go:106 +0x1d3
==================
```

```
panic: interface conversion: interface {} is nil, not types.TMEventData

goroutine 7690 [running]:
github.com/tendermint/tendermint/consensus.waitForAndValidateBlock.func1(0xc427727620, 0x3)
        /go/src/github.com/tendermint/tendermint/consensus/reactor_test.go:292 +0x62b
created by github.com/tendermint/tendermint/consensus.timeoutWaitGroup
        /go/src/github.com/tendermint/tendermint/consensus/reactor_test.go:349 +0xa4
exit status 2
FAIL    github.com/tendermint/tendermint/consensus      38.614s

```